Logging trailer

ABSTRACT

An extended trailer to attach to a tractor. The trailer has a main reach able to attach to a tractor. An extension reach extends rearwardly of the main reach. A bridge over the main is rigidly attached to the main reach. There is a forward self steering axle for the extended trailer. Springs extend forward from the bridge to the forward axle. The extension has an intermediate axle and rear axles. A subframe carries the intermediate and rear axles and is pivotally attached to the bridge.

FIELD OF THE INVENTION

This invention relates to an extended trailer, especially a trailer foruse in logging.

DESCRIPTION OF THE PRIOR ART

In logging a trailer able to carry long loads is required. The typicalarrangement used is a tractor trailer combination in which the traileris of simple construction. The load is, of course, self-supporting. Thetrailer has a central tubular reach able to attach to the tractor, withtwo axles at the rear, remote from the tractor. There are upstandingmembers to restrain the load from sideways movement and these upstandingmembers typically are mounted on pivotal bunks.

The trailer length is restricted by the small maneuvering capability ofa long, simple structure and by highway regulations. These regulationsrestrict vehicle weight and load-carrying capacity, the latter usuallydepending on the number of axles, wheels and the spaces between axles.

Examples of prior art structures known to applicant include U.S. Pat.Nos. 4,219,210 to Genberg; 2,034,842 to Stratton; 4,496,166 to Andersonand 2,112,201 to Larison.

Of the above Genberg discloses a logging trailer in which an auxiliarytrailer is towed behind a main trailer. The auxiliary trailer has apivot point that allows it to be carried by the main trailer.

Stratton shows a structure for self-loading the trailers of loggingtrucks. Anderson relates to a translotor log trailer of complicatedstructure. Larison again shows a complicated means of loading a traileronto a truck.

The above demonstrate the complicated structures that are available inlogging once the simple, poorly maneuverable, conventional trailer is tobe extended.

The present invention seeks to provide a trailer that is longer thanconventional trailers and thus of increased load-carrying ability Thetrailer of the invention is of an improved maneuverability and, in apreferred embodiment, has a leading axle on which the wheels areself-steering.

Accordingly the present invention is an extended trailer to attach to atractor and comprising:

a main reach;

means formed at the end of the main reach to attach to a tractor;

a bridge extending over the main reach;

a forward self steering axle for the extended trailer;

resilient means extending forward from the bridge to the forward axle;

an intermediate axle on the extension;

a rear axle on the extension; and

a subframe carrying the intermediate and rear axles pivotally attachedto the bridge.

In a preferred embodiment the invention is a trailer as above in whichthe forward axle includes steerable mountings for wheels.

In one aspect of this preferred embodiment the trailer has a steeringarm extending from one wheel mounting means;

a spring abutment on the axle, spaced from the steering arm; a springarm extending from the steering arm and slidably received in the springabutment; a spring received on the steering arm on each side of thespring abutment plate;

whereby the springs allow wheels attached to the forward axle to turn onapplication of a turning force but urge the wheels back to a straightahead position in the absence of a turning force.

Aspects of the invention are illustrated, merely by way of example, inthe accompanYing drawings in which:

FIG. 1 is a side elevation of a trailer according to the presentinvention;

FIG. 2 is a plan view of the trailer of FIG. 1;

FIG. 3 is a front elevation of the trailer according to the presentinvention;

FIG. 4 is a detail on the line 4--4 of FIG. 3;

FIG. 5 illustrates a detail of the preferred embodiment of thisinvention;

FIG. 6 is an end elevation of the trailer of FIG. 1; and

FIG. 7 is a partial side elevation of the trailer of FIG. 6.

The drawings show an extended trailer 2 to attach to a tractor 4. Thetrailer comprises a main reach 6 with means formed at the end of themain reach to attach to the tractor 4. A simple hook 8 is shown in FIG.2; bridge 12 extends over the main reach 6. The bridge 12 compriseslongitudinally spaced members 14 linked by cross members 16 although thedetails of its structure are immaterial. Bridge 12 is rigidly attachedto the main reach 6 as shown most clearly in FIG. 4.

There is a forward axle 18 for the extended trailer and resilient meansin the form of leaf springs 20, as most clearly shown in FIGS. 3 and 4,extend forwardly from the bridge 12 to the forward axle 18. The leafsprings are located by U-bolts 22 at each end.

There is an intermediate axle 24 on the trailer 2 and a rear axle 26.Both these axles 24 and 26 are provided with wheels 28 at each end. Thewheels 28 are freely rotatable on the axles 24 and 26, avoiding thenecessity of a differential or the like.

There is a sub-frame to carry the intermediate and rear axles 24 and 26pivotally attached to the bridge 12. This sub-frame compriseslongitudinal members 30 linking the intermediate and rear axles at bothsides of the reach 6. There are support members 32 extending from thelongitudinal members 30 to the bridge 12. The support members 32 and thelongitudinal members 30 are attached at 34. The support members 32 areattached to a mounting plate 36 spaced from bridge 12, typically byabout 2 inches. There are bearing blocks 38 attached to the mountingplate 36 to receive pivot pins 40, which are attached to the bridge 12.The bearing blocks 38 comprise upper 42 and lower members 44, the lowermembers 44 being attached to the upper members 42 by nuts 46 received onstuds 48. This is a conventional arrangement. The pivot pins 40 are thenreceived with a bearing fit within the bearing blocks 38.

There are load support means 50 extending from the bridge 12 and, inconventional manner, pivotally attached to a bunk 52 mounted on thebridge 12. The arrangement is most clearly shown in FIGS. 1 and 7 but isnot part of the present invention. These load support members 50 and thebunks 52 that permit their rotation are prior art.

In a particularly preferred embodiment of the invention the forward axle18 includes steerable mountings for wheels 54 mounted on axle 18. Thearrangement is such that the wheels 54 are self-steering, rather thanbeing activated by a linkage extending to the driver's cab. Inconventional manner the steerable wheels 54 are pivotal on the axle 18by the use, for example, of steering or king pins 56 extending fromhousings 58 on the hubs of wheel 54 through a bushing in forward axle18. There is a steering link 60 extending between the hubs of wheels 54in conventional manner to ensure that the wheels move in unison aboutthe pivotal steerable mountings 58.

The steering action is controlled by the provision of a steering arm 62extending from one wheel mounting as shown most clearly in FIGS. 4 and5. There is a spring abutment 64 on the axle 18, spaced from thesteering arm. A spring arm 66 extends from the steering arm 62 and isslidably received in the spring abutment 64. Spring 68 is received onthe steering arm 66 on each side of the spring abutment 64. Springs 68act to damp the wheel movement, acting to prevent the wheels changingsteering direction on encountering a bump and also acting to stablilizethe wheels in the straight-ahead position when the trailer is notturning.

Wheels 54 are self steering. They have castor and camber so that theycan turn as the vehicle turns and thus applies a turning force to thewheels 54. Their mounting is thus designed to allow castor and camberaction to steer them as the trailer turns.

A shock absorber or damper 70, preferably hydraulic, extends from thesteering arm 62 to damp the action of sppring 68. As shown in FIG. 5 itmay be attached to the steering arm 62 at one end and the body or pistonof the shock absorber is attached to the spring abutment 64 at its innerend.

The trailer of the present invention permits the carrying of loads ofincreased length and weight. The provision of pivotal joints and, inparticular, the provision of greatly increased wheel area permitsgreater loads than a conventional trailer. The use of pivotal jointsbetween the bridge and the sub-frame means that the trailer maintainscontact with the road at all times.

The trailer is made of conventional materials in the art, bearing inmind that the trailers are subjected to considerable loads and forces.

I claim:
 1. An extended trailer to attach to a tractor and comprising:amain reach; means formed at the end of the main reach to attach to atractor; a bridge extending over the main reach; a forward axle for theextended trailer; steerable mountings for wheels on the forward axle,the mounting having castor and camber; resilient means extending forwardfrom the bridge to the forward axle; an intermediate axle on theextension; a rear axle on the extension; and a subframe carrying theintermediate and rear axles pivotally attached to the bridge.
 2. Atrailer as claimed in claim 1 in which the bridge member comprisesspaced longitudinal members linked by cross members.
 3. A trailer asclaimed in claim 1 in which the resilient means are leaf springsattached to the bridge and the forward axle.
 4. A trailer as claimed inclaim 1 in which the subframe comprises longitudinal members linking theintermediate and rear axles at both sides of the extension; andsupportmembers extending from the longitudinal members to the bridge.
 5. Atrailer as claimed in claim 4 in which the support members are attachedto a mounting plate;pivot pins attached to the bridge; and bearingblocks attached to the mounting plate whereby the plate can pivot abouta transverse axis relative to the bridge.
 6. A trailer as claimed inclaim 1 including load support means extending from the bridge.
 7. Atrailer as claimed in claim 6 in which the load support means ispivotally attached to a bunk.
 8. A trailer as claimed in claim 1 inwhich the steerable mountings are pivotal on the axle.
 9. A trailer asclaimed in claim 8 including steering link extending between the wheelmounting means.
 10. A trailer as claimed in claim 9 having a steeringarm extending from one wheel mounting means;a spring abutment on theaxle, spaced from the steering arm; a spring arm extending from thesteering arm and slidably received in the spring abutment; a springreceived on the steering arm on each side of the spring abutment plate;whereby the spring will allow wheels attached to the forward axle toturn under the action of the castor and camber on application of aturning force but urge the wheels back to a straight ahead position inthe absence of a force.
 11. A trailer as claimed in claim 10 including ashock absorber extending from the steering arm to damp the springaction.